In the integrated circuit (IC) industry, known lithography methods (e.g., 193 nm excimer laser, pattern quadrupling, and extreme ultraviolet (EUV)) are reaching limits in the ability to pattern complicated IC features. This limit is due to the nature of the device structures, especially the smallest size or critical dimension (CD) of features, which dimension has been reduced with each technology generation for fabricating memory or logic devices, including complementary metal oxide semiconductor (CMOS) devices. For example, in some present day technologies, devices are defined by critical dimensions less than 100 nm, and in some cases less than 25 nm. Often the device or structure to be fabricated may be repeating structures such as linear structures (lines), where processing may involve changing the size (dimension) along one direction, such as the X-direction, or Y-direction, but not along both directions. Furthermore, in some instances a change in vertical direction (Z-direction) is to be minimized during processing. Therefore, improved control of X, Y, and Z dimensions for various structures including complicated structure shapes is useful, where control to less than 5 nm variation may be useful.
In addition to controlling of individual dimensions of devices along select directions, statistical process control may be useful to ensure repeatability of device dimensions across multiple different microscopic or nanoscopic devices, where such devices are distributed over a surface of a substrate over macroscopic distances, such as many centimeters.
To this end, Critical Dimension Scanning Electron Microscopy (CD-SEM) has be developed to evaluate and control device processing. Notably, the use of CD-SEM is relatively slow and expensive, requiring a wafer (substrate) to be transported from a processing apparatus being evaluated to a remote area of a fabricator. This transfer and evaluation entails reduced throughput, affecting cost of development of processing, as well as cost of manufacturing once a process has been implemented. Furthermore, measurement of the height of a line or other structure along the Z-direction, entails breaking a substrate.
It is with respect to these and other considerations the present embodiments are provided.